So I picked up a used 6.4 from a low mile manual car so no MDS and found a G238, did a leakdown test and it looks good so I'm going to try it as is. I am leaning towards the Jeep Speed Shop swap kit (I welcome any input here) but I have a couple of questions.
First, the flywheel clutch combo. It seems like people have used the Dakota setup and some the ram 2500/5.7 setup, just wondering what is the difference?
Second will the stock driveshafts work with this setup? I took a rough measurement of the 6.4/G238 combo and it seems slightly longer than existing.
No complaints here; just facts. I ordered my kit from JSS, over the phone, around March 20, 2017. I received the last of three shipments from them around November 6, 2017. If you go with them, then try to stick to the scope of the kit as much as possible. I wasn't happy with several of the kit parts, and only ended up using their frame brackets, transmission cross member plates, and battery tray. Also used a harness and pcm from them but in the end, they couldn't make their pcm work properly for this setup, so they had Chris at Hotwire Auto send me one of his. More on the electrical stuff below.
Recommend weld-in engine brackets. The bolt-in brackets use the original engine frame brackets, so the engine probably can't be moved around much to correct any fitment issues (think shift tower). There are a few businesses that sell them.
Recommend custom exhaust headers done after the engine is in place. The 6.4 will leave HP / TQ on the table if you use the GC log manifolds. Lots of extra work to make the stock SRT manifolds fit but obviously it can be done. Go local and have a shop fab a set on your jeep for best results. I think that would be ~1200 or so.
Highly recommend getting the air inlet out of the engine compartment. The stock SRT intake manifold leaves few options, but you can get a modified version to get the air inlet back over to the passenger (right) side. The modified intake (and also something like Edelbrock) is very $$$$, but the alternative is a vvt truck manifold (2009+ 5.7) and it costs almost as much after buying the truck timing cover and accessories. For my first couple of engine runs in the driveway, I had the hood up with the snorkel removed, about 80 degrees ambient; my intake air temp went all the way up to 144 degrees in 15 minutes.
I'm using stock flywheel and Centerforce clutch for the 2005-2009 Dakota 4.7. Not enough miles yet but so far so good (1500 miles). I do have a subtle rattling sound at idle / neutral but not sure if it's the clutch or something else.
Stock driveshafts work well. My TC is about 1/4" further back than stock. The rest of my drivetrain is stock (except cromoly rear axle shafts) and I haven't grenaded anything, but only street / daily driving so far. Recommend aftermarket driveshafts eventually (I need a new front - torn rzeppa boot - and will probably get a set made local in the next few weeks).
Get your harness and PCM straight from Hotwire Auto. One thing I'm just now experiencing is that the older NGC4 pcms don't have all of the engine control features that come on the current stock SRTs (which are GPEC-2 I think). Shouldn't be surprised, I guess, but just not sure if I'll ever reach the fuel efficiency of the newer SRT cars with the old computer. We'll see. You will also want to get a professional tuning package (HP tuners is what most of the cool kids are using today) and get it to a dyno when you've sorted out all the teething issues. I've put together a tune (using HPT) that seems to be working well now and can send to you, to help you set up your own "baseline" without too much objection from the jeep. I will get mine to a dyno for a fully custom tune but so far I'm all the way up to 13mpg lol.
Get a C&R radiator, and a 2012+ JK "pentastar" fan. I'm using Amsoil heavy duty engine coolant with no problems. Coolant voltage to ground stays right around 0.1V so electrolytic corrosion of the radiator doesn't appear to be a problem at all.
Last item (for now): cruise control probably won't work because the cars use the CAN C bus to send cruise control commands to the pcm; stock Jeep JK uses direct wiring to the pcm. I'm working on a Franken-fix for this and will let you know if it works.
Good luck! Let us know how it goes.
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